This is exactly analogous to the gravitational force in the absence of dissipative forces such as friction. The electrostatic or Coulomb force is conservative, which means that the work done on q is independent of the path taken. Let us explore the work done on a charge q by the electric field in this process, so that we may develop a definition of electric potential energy. It is as if the charge is going down an electrical hill where its electric potential energy is converted to kinetic energy. The process is analogous to an object being accelerated by a gravitational field. When a free positive charge q is accelerated by an electric field, such as shown in Figure 1, it is given kinetic energy.

Work is done by a force, but since this force is conservative, we can write W = –ΔPE. In both cases potential energy is converted to another form. A charge accelerated by an electric field is analogous to a mass going down a hill.